EXSS is Exercising Science Solutions for Public Impact

Muscle Characteristics and Body Composition of NCAA Division I Football Players

Body composition has become an important part of athlete assessment. The amount of muscle and fat an athlete has can be predictive of performance, and bone mass assessment is important for understanding if developmental problems exist or if the athlete will face current or future risk for fracture or other injury. A periodic assessment of body composition and muscle characteristics may also help the athlete understand if the training regimen is causing the kinds of physical changes that are being sought. Thus, identifying ways to quantify various aspects of body composition and muscle is important for optimizing performance and reducing injury risk during sport and physical activity.

This week we highlight the work of Malia Melvin, who graduated from our masters program in Exercise Physiology in 2014. Under the direction of her thesis committee (Dr. Abbie Smith-Ryan, Dr. Eric Ryan, and Eric Sobolewski), Malia examined novel methods of body composition and muscle characteristics in varsity football athletes. Many thanks to Malia and Dr. Smith-Ryan for contributing to this week’s EXSS Impact blog post.

Image-J software outline of a B-mode ultrasound scan of the vastus lateralis to determine muscle cross-sectional area and echo intensity.

1) Why did you do the study?

Current research studies investigating body composition of collegiate football players have used a variety of devices and two-compartment models such as air displacement plethysmography (BODPOD), hydrostatic weighing, and skinfolds. In addition, there is limited research investigating muscle characteristics such as muscle cross sectional area (CSA) and muscle quality as measured by echo intensity in an athletic population. Therefore, the current study aimed to examine additional body and muscle composition characteristics by using a B-mode ultrasound for muscle CSA and echo intensity, as well as a three-compartment model, dual energy x-ray absorptiometry (DEXA), which provides regional lean and fat mass.

Individual comparisons of lean mass (kg) and fat mass (kg) stratified by player position

2) What did you do and what did you find?

For this study, sixty-nine Divison I football players volunteered to participate. Subjects were stratified by player position: defensive linemen, offensive linemen, quarterbacks, running backs, wide receivers, tight ends, linebackers, defensive backs, and kickers/punters. Players were also stratified by race, year classification, and starter status. Muscle cross sectional area and echo intensity of the vastus lateralis were determined from a panoramic scan performed at the midpoint of the thigh using a B-mode ultrasound. The ultrasound probe was held perpendicular to the tissue and swept across the skin at equal pressure from the lateral vastus lateralis border to the medial fascia separation. From the panoramic scan, muscle CSA and echo intensity were then estimated using ImageJ software by tracing along the fascial border of the muscle using the standard histogram function. Body composition measures including whole body and regional fat mass, lean mass, and percent fat were determined by the DEXA. Measures of muscle CSA, percent fat, lean mass, and fat mass were found to be significantly different across position, likely due to the differences in position-specific tasks. However, no differences between positions were observed for EI measures, which may indicate competitive athletes have increased muscle quality regardless of body size and composition differences.

3) What’s the impact of these findings on the public?

As ultrasound devices are readily available in most athletic facilities as a clinical tool, it may provide other practical measures for athletes, athletic trainers, and strength coaches. Ultrasound and DEXA measures may provide beneficial reference information of regional fat mass, lean mass, and muscle quality when adapting training or nutrition regiments as a result of season, weight goals, or injury. Recognizing muscle imbalances with Ultrasound or DEXA measures may also improve the quality of resistance exercise prescription, and help determine whether an injured athlete is ready to return to play. The addition of muscle CSA and echo intensity, combined with body composition values may be important for athletes considered “at risk” due to high percent fat or injury status.